The Official List of Rejected Suggestions wrote:

3.2 Disable remixing or censor minor remixes
One of the most important ideas of Scratch is the share aspect. Scratch is a website not only for displaying your work, but also for sharing it with others, and by posting your project on the Scratch website you agree to allow others to remix your work. This includes allowing others to use the backpack to use your creations in their own projects. You are not allowed to write “Do not remix this project” in the Notes and Credits of your project; you may get alerted for this, because it discourages remixing. This suggestion extends to the ability to require permission to remix a project, as you have already given permission to others to use your creations by sharing a project on Scratch; for more information, see this post.

A remix of a project is allowed on Scratch, even if the remix only contains minor changes (this includes recolors). However, when you remix a project, you should put in the Notes and Credits what you changed. If you see a project that contains no noticeable changes, please use the Report button on it so the Scratch Team can take a look at it. This suggestion extends to “extremely minor remixes,” such as a remix of a game that gives you 2 points per second instead of 1. As long as the user explains what they changed about the project and gives proper credit, this is okay.

However, a feature that prevents unchanged remixes from being shared is NOT rejected. You can discuss it on this topic.